The present invention relates to surface inspection systems and methods and, more particularly, to the inspection of articles or workpieces, such as silicon wafers, to detect the presence of defects such as particles or pits on the surface and to distinguish therebetween.
Surface inspection systems are commonly used for the inspection of articles or workpieces such as silicon wafers to detect the presence of defects on the wafer surface. When the inspection indicates a large number of defects, the wafer may be sent back for recleaning. If the defects are particles or other debris on the wafer surface, the recleaning is successful. However, if the defects are pits or "COPS" (crystal originated pits) in the wafer surface, they are not removed by recleaning. Because such surface inspection systems fail to distinguish between pit defects and particle defects, the wafer is typically sent back for recleaning regardless of whether the defects are pits or particles. Because these defects may be pits, recleaning the wafer may result in nothing more than a waste of time and resources. It would be advantageous to be able to distinguish pits in the surface of the wafer from particles located thereon.